1. Field of the Invention
The present invention relates to a self-adjustable cable tensioning device for removing slack from a cable used in a parking brake of a motor vehicle.
2. Description of the Related Art
As typical examples of a device for self-adjusting a length of a cable in a parking brake of a motor vehicle, a hand brake with an adjusting device for a motor vehicle is disclosed in U.S. Pat. No. 5,272,935, and a variable ratio parking brake lever with self-adjust cable tensioning means is disclosed in U.S. Pat. No. 5,448,928. In these examples, as a pawl is disengaged from ratchet teeth formed on a circumferential outer surface of a rotating plate, the rotating plate is rotated by means of a take-up spring so as to take up a cable thereon by a slacked length thereby to self-adjustably maintain the cable in an adequately tensioned status.
However, the conventional devices constructed as mentioned above suffer from defects in that, when the pawl is engaged with and disengaged from the ratchet teeth, noise is generated, and, since this noise is provoked independently of skillfulness of a driver, uncomfortableness is caused to the driver in the course of manipulating the hand brake or the parking brake lever. Also, because ineffective tensioning stroke of the rotating plate can be induced at the maximum by a pitch of a ratchet tooth, it is difficult to precisely tension the cable by the slacked length, whereby it is impossible to hold a constant braking point.
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a self-adjustable cable tensioning device for a parking brake of a motor vehicle, which does not generate noise when removing slack from a cable, and can precisely maintain the cable in an adequately tensioned status without experiencing ineffective tensioning stroke.
In order to achieve the above object, according to the present invention, there is provided a self-adjustable cable tensioning device for a parking brake of a motor vehicle. In the device, a mounting bracket is fastened to a body of the motor vehicle and has an engaging pin. A hand lever is pivotally mounted to the mounting bracket in such a way as to be moved between a brake-applied position and a brake-released position. A detaining plate is secured to a side of the hand lever. A rotating plate is fitted around the detaining plate in a manner such that the rotating plate can be rotated along with or independently of the detaining plate. The rotating plate has integrated therewith a cable guide bracket. The detaining plate and the rotating plate cooperate with each other to define therebetween a plurality of actuating chambers which are spaced apart one from another by a predetermined angle and each of which is gradually narrowed in a clockwise direction. A plurality of rollers are inserted into the plurality of actuating chambers in a manner such that the rollers can be locked into and unlocked from narrowed parts of the actuating chambers, respectively. The rollers are actuated by an actuating plate. A spring biases the actuating plate in the clockwise direction to maintain the rollers in a locked status when the hand lever is in the brake-applied position. The actuating plate is engaged with the engaging pin of the mounting bracket immediately before the hand lever reaches the brake-released position, thereby to allow the rollers to be unlocked from the narrowed parts of the actuating chambers, respectively. At a consequence, as the cable guide bracket which is integrated with the rotating plate, is rotated by a take-up spring, slack of a cable can be removed.